Polyalkylene oxide particles and production method for the same

ABSTRACT

The present invention relates to a production method of polyalkylene oxide particles including a step of forming the polyalkylene oxide particles by polymerization of an alkylene oxide in a polymerization solution containing a polymerization solvent and a catalyst dispersed in the polymerization solvent. The average particle diameter of the catalyst is more than 25 μm.

TECHNICAL FIELD

The present invention relates to polyalkylene oxide particles and aproduction method for the same.

BACKGROUND ART

A polyalkylene oxide is water-soluble and thermoplastic, therefore, thepolyalkylene oxide is used for uses such as a viscous agent forpapermaking, a ceramic binder, a polymerization stability assistant anda material for a pharmaceutical preparation. When the polyalkylene oxideis used as a thickener such as a viscous agent for papermaking and thelike, generally, the polyalkylene oxide having a high molecular weightis preferable from the viewpoint of a viscosity control. As a productionmethod of the polyalkylene oxide having a high molecular weight, amethod using a catalyst obtained by the reaction of an organozinccompound with an aliphatic polyhydric alcohol and a monohydric alcoholhas been reported (refer to patent literature 1).

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Application PublicationNo. H5-17566

SUMMARY OF INVENTION Technical Problem

However, it was found that the polyalkylene oxide obtained by theproduction method disclosed in patent literature 1 tends to be difficultto be dispersed into or dissolved in a medium such as water, when it isused as a mucilaginous agent for papermaking for example.

Accordingly, an object of the present invention is to providepolyalkylene oxide particles having an excellent dispersibility in amedium such as water and a production method thereof.

Solution to Problem

The present invention relates to a production method of polyalkyleneoxide particles comprising forming polyalkylene oxide particles bypolymerization of an alkylene oxide in a polymerization solutioncontaining a polymerization solvent and a catalyst dispersed in thepolymerization solvent (polymerization step). The average particlediameter of the catalyst is more than 25 μm.

The polyalkylene oxide particles obtained by the above-describedproduction method have an excellent dispersibility in a medium such aswater.

It is preferable that the catalyst is an organozinc catalyst.Furthermore, it is preferable that the organozinc catalyst is aparticulate reaction product obtainable by a method including: reactingan organozinc compound with an aliphatic polyhydric alcohol and amonohydric alcohol thereby forming a particulate reaction product(reaction step).

When a polymerization solution contains such an organozinc catalyst, themolecular weight of a polyalkylene oxide can be controlled to be higher.

It is preferable that the polymerization solution contains 0.00005 molor more of the catalyst with respect to 1 mol of an alkylene oxide. Whenthe used amount of the catalyst is in the above-described range, thedecrease in a polymerization reaction rate can be suppressed andpolymerization time can be controlled to be shorter.

The present invention also relates to polyalkylene oxide particlesobtainable by the above-described production method. The proportion ofparticles having a particle diameter less than 150 μm in thepolyalkylene oxide particles according to the present invention is lessthan 40% by mass.

Advantageous Effects of Invention

The polyalkylene oxide particles obtainable by the above-describedproduction method have an excellent dispersibility in a medium such aswater. Furthermore, the polyalkylene oxide particles are excellent insolubility in a medium such as water since the polyalkylene oxideparticles are less likely to aggregate.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, the embodiments of the present invention will be described.However, the present invention is not limited to the followingembodiments.

The production method of the polyalkylene oxide particles according tothe embodiments comprising: forming polyalkylene oxide particles bypolymerization of an alkylene oxide in a polymerization solutioncontaining a polymerization solvent and a catalyst dispersed in thepolymerization solvent.

The alkylene oxide may be at least one kind selected from a groupconsisting of ethylene oxide, propylene oxide, butylene oxide,cyclohexene oxide, styrene oxide and epichlorohydrin, for example. Amongthese alkylene oxides, ethylene oxide or propylene oxide are preferablyused since the solubility to water of the obtained polyalkylene oxide ishigh. These alkylene oxides may be used alone respectively, or two ormore kinds may be used in combination.

The polymerization solvent may be at least one kind of a hydrocarbonsolvent of selected from a group consisting of n-pentane, n-hexane,n-heptane and cyclohexane, for example. Among these polymerizationsolvents, n-hexane or n-pentane is preferably used from the viewpointthat these solvents have easy industrial availability, the boilingpoints thereof are lower than the melting point of the obtainedpolyalkylene oxide and after the polymerization reaction, these solventscan be easily removed. These polymerization solvents may be used alonerespectively, or two or more kinds may be used in combination.

The used amount of the polymerization solvent is preferably 200 parts bymass to 10000 parts by mass and more preferably 400 parts by mass to 600parts by mass with respect to 100 parts by mass of an alkylene oxidefrom the viewpoint of the easy removal of the heat of polymerization andthe easy control of a polymerization reaction.

Usually, the catalyst in the embodiment is a particulate. The averageparticle diameter of the catalyst is more than 25 μm, preferably 30 μmto 50 μm and more preferably 35 μm to 45 μm. When the average particlediameter of the catalyst is 25 μm or less, there is tendency that theparticle diameter of the obtained polyalkylene oxide particles is small,swelling of the particulate in a medium such as water is fast and a poordispersion in the medium occurs. The value of the average particlediameter of the catalyst is measured by a laser diffraction method to bedescribed below.

It is preferable that the catalyst is an organozinc catalyst from theviewpoint of obtaining the polyalkylene oxide having a high molecularweight. It is preferable that the organozinc catalyst as a catalyst is aparticulate reaction product of obtainable by a method including:reacting an organozinc compound with an aliphatic polyhydric alcohol anda monohydric alcohol, thereby forming a particulate reaction product.

The organozinc compound to be used for obtaining the organozinc catalystis a compound represented by a general formula, ZnR₂ (R represents amonovalent organic group), for example. Examples of R include an alkylgroup having 1 to 6 carbon atoms, a phenyl group and a cycloalkyl grouphaving 4 to 6 carbon atoms. Specific examples of the organozinc compoundinclude dialkyl zincs such as dimethyl zinc, diethyl zinc, di-n-propylzinc and di-n-butyl zinc, diphenyl zinc, dicyclobutyl zinc and the like.These organozinc compounds may be used alone respectively, or two ormore kinds may be used in combination.

The aliphatic polyhydric alcohol to be used for obtaining a particulatereaction product described above as an organozinc catalyst is analiphatic alcohol having 2 or more hydroxyl groups and 2 or more carbonatoms. The aliphatic polyhydric alcohol may be at least one kindselected from a group consisting of ethylene glycol, propylene glycol,1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol,1,5-pentanediol, 2,3,4-pentanetriol, glycerine and pentaerythritol, forexample. The aliphatic polyhydric alcohol is preferably an aliphaticpolyhydric alcohol having 4 carbon atoms from the viewpoint of obtainingthe polyalkylene oxide having a high molecular weight. Examples of thealiphatic polyhydric alcohol having 4 carbon atoms include1,3-butanediol and 1,4-butanediol. These aliphatic polyhydric alcoholsmay be used alone respectively, or two or more kinds may be used incombination.

The used amount of the aliphatic polyhydric alcohol is preferably 0.1mol to 1.1 mol and more preferably 0.3 mol to 0.9 mol with respect to 1mol of the organozinc compound. When the used amount of the aliphaticpolyhydric alcohol is less than 0.1 mol with respect to 1 mol of theorganozinc compound, there is a possibility that it takes long time toreact due to extreme decrease of the polymerization reaction rate, whichis economically disadvantageous. When the used amount of the aliphaticpolyhydric alcohol is more than 1.1 mol with respect to 1 mol of theorganozinc compound, there is a possibility that the obtainedpolyalkylene oxide particles cohere to agglomerate.

The monohydric alcohol to be used for obtaining a particulate reactionproduct described above as the organozinc catalyst is an alcohol whichhas one hydroxyl group and does not have an active hydrogen other thanthe active hydrogen of the hydroxyl group. The monohydric alcohol may beat least one kind selected from a group consisting of primary alcoholssuch as methanol, ethanol, 1-propanol and 1-butanol; secondary alcoholssuch as 2-propanol and 2-butanol; and tertiary alcohols such ast-butanol, for example. The monohydric alcohol is preferably amonohydric alcohol having 1 to 6 carbon atoms among them from theviewpoint of obtaining the polyalkylene oxide having a high molecularweight. Examples of the monohydric alcohol having 1 to 6 carbon atomsinclude ethanol, propanol and butanol. These monohydric alcohols may beused alone respectively, or two or more kinds may be used incombination.

The used amount of the monohydric alcohol is preferably 1 mol or more,more preferably 2 mol to 15 mol and further more preferably 4 mol to 12mol with respect to 1 mol of the organozinc compound. When the usedamount of the monohydric alcohol is less than 1 mol with respect to 1mol of the organozinc compound, there is a tendency that thepolymerization reaction of an alkylene oxide is not smoothly preceded.When the used amount of the monohydric alcohol is more than 15 mol withrespect to 1 mol of the organozinc compound, there is a tendency thatthe time required for removal is increased due to increase of the amountto be removed when an unreacted alcohol is removed as described below.

Molar ratio of a monohydric alcohol with respect to an aliphaticpolyhydric alcohol is calculated as “moles of a monohydric alcohol/molesof an aliphatic polyhydric alcohol”. The molar ratio is preferably 2 ormore and more preferably 4 to 50. When the molar ratio is less than 2,there is a tendency that the polymerization reaction of an alkyleneoxide is not smoothly preceded. When the molar ratio is more than 50,there is a tendency that the time required for removal is increased whenan unreacted alcohol is removed as described below. As the molar ratiois increased, there is a tendency that the average particle diameter ofthe obtained catalyst is increased.

The method for reacting an organozinc compound with an aliphaticpolyhydric alcohol and a monohydric alcohol is not particularly limited.For example, the reaction can be carried out by (1) a method in whichafter an organozinc compound is reacted with a monohydric alcohol, theproduct is reacted with an aliphatic polyhydric alcohol, (2) a method inwhich after an organozinc compound is reacted with an aliphaticpolyhydric alcohol, the product is reacted with a monohydric alcohol and(3) a method in which an organozinc compound is reacted with analiphatic polyhydric alcohol and a monohydric alcohol at the same time.Among these methods, (3) a method in which an organozinc compound isreacted with an aliphatic polyhydric alcohol and a monohydric alcohol atthe same time is particularly preferable from the viewpoints of easyhandleability.

Usually, the reaction of an organozinc compound with an aliphaticpolyhydric alcohol and a monohydric alcohol is carried out in a reactionsolution containing a solvent for preparing a catalyst under an inertgas atmosphere from the viewpoint of carrying out a reaction smoothly.

As a solvent for preparing a catalyst, hydrocarbon solvents such asn-pentane, n-hexane, n-heptane and cyclohexane are exemplified. Amongthese solvents for preparing a catalyst, n-hexane or n-heptane arepreferably used from the viewpoint that these solvents have easyindustrial availability, the quality thereof is stable and the pricesthereof are low. These solvents for preparing a catalyst may be usedalone respectively, or two or more kinds may be used in combination.

The inert gas is not particularly limited as long as it is a gas thatunlikely inactivates the obtained organozinc catalyst. For example,nitrogen gas, argon gas and helium gas are exemplified.

When an organozinc compound is reacted with an aliphatic polyhydricalcohol and a monohydric alcohol, preferably, an aliphatic polyhydricalcohol and a monohydric alcohol are supplied as a mixture thereof orseparately to a reaction solution containing an organozinc compound andthe above-described solvent. Supply (addition) rate into the reactionsystem (reaction solution) of an aliphatic polyhydric alcohol or amonohydric alcohol is preferably 10 g/min or less and more preferably 2g/min or less. When the supply rate is 10 g/min or less, there is atendency that the particle size distribution of the obtained catalystcan be controlled to be narrower. In addition, the temperature of thereaction system (reaction solution) at the time of supplying analiphatic polyhydric alcohol or a monohydric alcohol into the reactionsystem is preferably 0° C. to 60° C.

After supplying an aliphatic polyhydric alcohol and a monohydric alcoholinto the reaction system, the temperature of reaction system may bechanged and may be adjusted to other temperatures (reaction temperature)in order to proceed the reaction of an alcohol with an organozinccompound. The reaction temperature is generally 0° C. to 200° C. andpreferably 20° C. to 200° C. The reaction time, for example, is 0.5hours to 10 hours.

The reaction solution containing an organozinc compound, an aliphaticpolyhydric alcohol and a monohydric alcohol is preferably stirred.Stirring can be carried out by a well-known method. The stirring rate ispreferably low. When the stirring rate is low, there is a tendency thatthe average particle diameter of the obtained catalyst is increased.

The catalyst is obtained in a state of a dispersion dispersed in asolvent for preparing the catalyst, an unreacted aliphatic polyhydricalcohol and a monohydric alcohol and the like. An unreacted alcohol ispreferably removed from the dispersion from the viewpoint of carryingout a polymerization reaction smoothly. The catalyst is preferablysupplied to a polymerization reaction in a state of a dispersioncontaining substantially only a solvent for preparing the catalyst as adispersion medium from the viewpoint of suppressing inactivation of thecatalyst.

The polymerization solution preferably contains 0.00005 mol or more of acatalyst and more preferably 0.0001 mol to 0.0006 mol with respect to 1mol of an alkylene oxide. When the used amount of the catalyst is lessthan 0.00005 mol with respect to 1 mol of an alkylene oxide, there is apossibility that it takes long time to polymerize due to extremedecrease of the polymerization reaction rate.

The method for polymerizing an alkylene oxide in a polymerizationsolution containing a polymerization solvent and a catalyst dispersed inthe polymerization solvent is not particularly limited. For example, thepolymerization solvent and the catalyst are added into a polymerizationreaction vessel and an alkylene oxide is further added to prepare thepolymerization solution, and the alkylene oxide can be polymerized withstirring the polymerization solution under an inert gas atmosphere.Usually the polymerization reaction is carried out with stirring thepolymerization solution from the viewpoint of increasing polymerizationreaction efficiency and suppressing agglomeration of polyalkylene oxideparticles.

The inert gas to be used in polymerization reaction is not particularlylimited as long as it is a gas that unlikely inactivates the catalyst.For example, nitrogen gas, argon gas and helium gas are exemplified.

The polymerization temperature of the polymerization reaction(temperature of a polymerization solution) is generally 5° C. to 100° C.and preferably 20° C. to 50° C. The reaction time of the polymerizationreaction is generally 0.5 hours to 10 hours.

After the polymerization reaction is completed, for example, by dryingthe product collected by filtration, the powder of polyalkylene oxideparticles is obtained.

Thus, the obtained polyalkylene oxide particles usually are made up of aplurality of particles (primary particles) having a different particlediameter. In particular, the polyalkylene oxide particles according tothe embodiment characteristically have the low content of particleshaving a small particle diameter. In the polyalkylene oxide particles,the proportion of particles having a particle diameter of less than 150μm is preferably less than 40% by mass, more preferably less than 30% bymass, further preferably less than 20% by mass and particularlypreferably less than 10% by mass from the viewpoint of dispersibilityand solubility in a medium such as water. The lower limit of theproportion of particles having a particle diameter less than 150 μm isnot particularly limited and may be 0% by mass. The values of the masspercentage of particles having a particle diameter less than 150 μm inthe polyalkylene oxide particles (particle size distribution) can bemeasured by a mesh passing type classification method described below.There are many cases in which the above-described particle diametercorresponds to primary particle diameter of the polyalkylene oxideparticles.

In the particle size distribution of the obtained polyalkylene oxideparticles, the proportion of small particles is decreased by using acatalyst having a specific average particle diameter in the productionprocess of the polyalkylene oxide particles of the present embodiment.As a result, the dispersibility and the solubility of the polyalkyleneoxide particles in a medium such as water are improved.

EXAMPLES

Hereinafter, the present invention will be described in detail usingPreparation Examples, Examples and Comparative Examples. However, thepresent invention is not limited to the following Examples.

[Evaluation Method]

The catalyst obtained in Preparation Examples and the polyalkylene oxideparticles obtained in Examples were evaluated according to the followingmethod.

(1) Average Particle Diameter of Catalyst

The average particle diameter of the catalyst is measured by a laserdiffraction method to be described below.

A catalyst slurry was prepared using hexane as a carrier. The catalystslurry was circulated in a laser diffraction type particle sizedistribution measuring apparatus (manufactured by Shimadzu Corporation,model: SALD-7100) and the average particle diameter of the catalyst wasmeasured.

(2) Particle Size Distribution and Mass Average Particle Diameter ofPolyalkylene Oxide Particles

The particle size distribution and the mass average particle diameter ofpolyalkylene oxide particles were measured and calculated by a meshpassing type classification method described below.

100 g of polyalkylene oxide particles and 2 g of amorphous silica(manufactured by Tokuyama Corporation, Tokusil NP) as a lubricant weremixed.

As a JIS Z 8801-1 standard sieve, sieves having 500 μm, 300 μm, 250 μm,180 μm, 150 μm, 106 μm and 75 μm of sieve opening were stacked on asaucer in this order from the top.

The mixture of the polyalkylene oxide particles and the amorphous silicawas put into a sieve having 500 μm of sieve opening placed at the top.The mixture was classified by shaking the sieve for 20 minutes using aRo-tap type shaker.

After the classification was completed, the mass of polyalkylene oxideparticles remained on each sieve was measured and the mass percentagewith respect to the total amount of each mass was calculated. The masspercentage was integrated in order from the sieve having a large openingsize to the sieve having a small opening size, and the relationshipbetween the opening size of the sieve and the integrated value of themass percentage (integrated mass percentage) of the polyalkylene oxideparticles remained on the sieve was plotted on a logarithmic probabilitypaper. The plot on the paper was connected by a straight line and thevalue of the opening size of the sieve when the integrated masspercentage is 50% by mass was regarded as the mass average particlediameter of the polyalkylene oxide particles.

Furthermore, the total value of the mass percentage of the polyalkyleneoxide particles remained on the sieve having 106 μm of sieve opening,the sieve having 75 μm of sieve opening and the saucer was calculated asthe mass percentage of particles having a particle diameter less than150 μm.

(3) Dispersibility of Polyalkylene Oxide Particles in Water

500 g of deionized water was put into a beaker of 1000 mL and thetemperature of the deionized water was adjusted to 25° C. 2.5 g ofpolyalkylene oxide particles was put thereto at one time with stirringthe deionized water in the beaker at a rotation speed of 250 rpm using astirrer equipped with a 2 blade upright type paddle (blade diameter: 80mm). After stirring for 10 seconds, the stirring was stopped. Then, thedispersion state of polyalkylene oxide particles in the beaker wasvisually observed. The dispersibility was evaluated according to thefollowing criteria. In the following criteria, “big aggregates” meanscoarse aggregates enough to be visually confirmed.

A: the number of big aggregates is 0 (none)

B: the number of big aggregates is 1 to 2

C: the number of big aggregates is 3 to 4

D: the number of big aggregates is 5 or more

Preparation Example 1 Catalyst A

A flask having an inner diameter of 80 mm and a volume of 500 mLequipped with a reflux condenser, a dropping funnel, a nitrogen gasinlet tube and an impeller having four paddle blades (inclination of)45° of a blade diameter of 53 mm as a stirrer was prepared.

After replacing the inside of the flask with a nitrogen gas, 56.3 g ofn-hexane (manufactured by Sumitomo Chemical Co., Ltd., high purity forindustrial use) and 9.9 g of an aliphatic hydrocarbon (manufactured byNippon Oil Co., Ltd., trade name: No. 0 solvent) having a high boilingpoint were added into the flask, and 9.9 g (80 mmol) of diethyl zinc(manufactured by Nippon Aluminum Alkyls, Ltd.) was further addedthereto. The reaction solution in the flask was cooled to 10° C. and wasstirred at the tip peripheral speed of 0.97 m/sec (stirring rotationspeed of 350 rpm).

Then, the total amount of the mixed solution of 6.5 g (72 mmol) of1,4-butanediol and 29.0 g (629 mmol) of ethanol was added into the flaskat the addition rate of 0.5 g/min using a dropping funnel. After theaddition was completed, the temperature of the inside of the flask waselevated up to 30° C. and diethyl zinc was reacted with 1,4-butanedioland ethanol for 1 hour. And after the temperature was elevated up to 50°C., the reaction was further carried out for 1 hour.

Thereafter, the temperature of the inside of the flask was elevated upto 140° C. and the unreacted alcohol was distilled off from the systemalong with n-hexane. After being cooled, the reaction solution in theflask was diluted with 400 ml of n-hexane to obtain 302 g of adispersion containing 3% by mass of an organozinc catalyst (catalyst A).The measurement results of the average particle diameter of the obtainedcatalyst A are shown in Table 1.

Preparation Example 2 Catalyst B

An operation was carried out in the same manner as Preparation Example 1except that the tip peripheral speed was changed from 0.97 m/sec(stirring rotation speed of 350 rpm) to 0.55 m/sec (stirring rotationspeed of 200 rpm), thereby obtaining 302 g of a dispersion containing 3%by mass of an organozinc catalyst (catalyst B). The measurement resultsof the average particle diameter of the obtained catalyst B are shown inTable 1.

Preparation Example 3 Catalyst C

An operation was carried out in the same manner as Preparation Example 1except that the tip peripheral speed was changed from 0.97 m/sec(stirring rotation speed of 350 rpm) to 1.94 m/sec (stirring rotationspeed of 700 rpm), thereby obtaining 302 g of a dispersion containing 3%by mass of an organozinc catalyst (catalyst C). The measurement resultsof the average particle diameter of the obtained catalyst C are shown inTable 1.

Preparation Example 4 Catalyst D

An operation was carried out in the same manner as Preparation Example 2except that the used amount of 1,4-butanediol was changed from 6.5 g (72mmol) to 2.2 g (24 mmol), thereby obtaining 302 g of a dispersioncontaining 3% by mass of an organozinc catalyst (catalyst D). Themeasurement results of the average particle diameter of the obtainedcatalyst D are shown in Table 1.

Preparation Example 5 Catalyst E

An operation was carried out in the same manner as Preparation Example 1except that the used amount of ethanol was changed from 29.0 g (629mmol) to 17.6 g (382 mmol), thereby obtaining 302 g of a dispersioncontaining 3% by mass of an organozinc catalyst (catalyst E). Themeasurement results of the average particle diameter of the obtainedcatalyst E are shown in Table 1.

TABLE 1 Condition of catalyst preparation Average Tip peripheralparticle speed Alcohol Addition rate Temperature in diameter [m/sec]ratio [g/min] system [° C.] [μm] Preparation Catalyst A 0.97 8.7 0.5 1035 Example 1 Preparation Catalyst B 0.55 8.7 0.5 10 45 Example 2Preparation Catalyst C 1.94 8.7 0.5 10 30 Example 3 Preparation CatalystD 0.55 26.2 0.5 10 53 Example 4 Preparation Catalyst E 0.97 5.3 0.5 1025 Example 5

In Table 1, alcohol ratio represents a molar ratio of a monohydricalcohol (ethanol) with respect to an aliphatic polyhydric alcohol(1,4-butanediol). The addition rate represents an addition (supply) rateinto the inside of the system (into flask) of the mixed solution of analiphatic polyhydric alcohol and a monohydric alcohol. The temperaturein system represents a temperature of the inside of the system (reactionsolution) when the mixed solution of an aliphatic polyhydric alcohol anda monohydric alcohol is supplied into the system.

Example 1

A pressure resistant reaction vessel of an inner diameter of 94 mm and avolume of 1 L which is provided with a dropping funnel, a nitrogen gasinlet tube and an impeller having an anchor type paddle blade of a bladediameter of 47 mm was prepared.

After replacing the inside of the pressure-resistant reaction vesselwith a nitrogen gas, 345 g of n-hexane (manufactured by SumitomoChemical Co., Ltd., high purity for industrial use) as a polymerizationsolvent was added into the reaction vessel and 3.1 g of a dispersion ofcatalyst A obtained in Preparation Example 1 was added thereto understirring to disperse uniformly, thereby obtaining a polymerizationsolution.

Next, 81 g (1.84 mol) of ethylene oxide was added to the polymerizationsolution. Thereafter, the temperature of the polymerization solution waselevated up to 30° C. and the polymerization of ethylene oxide wascarried out for 6 hours.

After the polymerization reaction was completed, the product wasseparated from n-hexane by filtration and 80.5 g of polyethylene oxideparticles was obtained by drying under reduced pressure at 40° C. for 5hours. The yield of the obtained polyethylene oxide particles was 99.3%by mass with respect to ethylene oxide. The evaluation of the massaverage particle diameter and the dispersibility in water of theobtained polyethylene oxide particles was carried out. The evaluationresults are described in Tables 2 and 3.

Example 2

80.7 g of polyethylene oxide particles was obtained in the same manneras Example 1 except that the dispersion of the catalyst A was changed tothe dispersion of the catalyst B. The yield of the obtained polyethyleneoxide particles was 99.6% by mass with respect to ethylene oxide. Theevaluation of the mass average particle diameter and the dispersibilityin water of the obtained polyethylene oxide particles was carried out.The evaluation results are described in Tables 2 and 3.

Example 3

80.3 g of polyethylene oxide particles was obtained in the same manneras Example 1 except that the dispersion of the catalyst A was changed tothe dispersion of the catalyst C. The yield of the obtained polyethyleneoxide particles was 99.1% by mass with respect to ethylene oxide. Theevaluation of the mass average particle diameter and the dispersibilityin water of the obtained polyethylene oxide particles was carried out.The evaluation results are described in Tables 2 and 3.

Example 4

80.3 g of polyethylene oxide particles was obtained in the same manneras Example 1 except that the dispersion of the catalyst A was changed tothe dispersion of the catalyst D. The yield of the obtained polyethyleneoxide particles was 99.1% by mass with respect to ethylene oxide. Theevaluation of the mass average particle diameter and the dispersibilityin water of the obtained polyethylene oxide particles was carried out.The evaluation results are described in Tables 2 and 3.

Comparative Example 1

80.4 g of polyethylene oxide particles was obtained in the same manneras Example 1 except that the dispersion of the catalyst A was changed tothe dispersion of the catalyst E. The yield of the obtained polyethyleneoxide particles was 99.3% by mass with respect to ethylene oxide. Theevaluation of the mass average particle diameter and the dispersibilityin water of the obtained polyethylene oxide particles was carried out.The evaluation results are described in Tables 2 and 3.

TABLE 2 Mass percentage of particles on each sieve [% by mass] Mass(particle size distribution) average Opening Opening Opening OpeningOpening Opening Opening particle Catalyst size size size size size sizesize diameter type 500 μm 300 μm 250 μm 180 μm 150 μm 106 μm 75 μmSaucer [μm] Example 1 Catalyst A 7.1 37.9 29.0 24.8 0.5 0.5 0.1 0.1 291Example 2 Catalyst B 24.0 40.4 9.2 17.1 4.6 2.1 0.4 2.2 357 Example 3Catalyst C 8.6 2.9 23.2 60.5 3.4 1.1 0.2 0.1 235 Example 4 Catalyst D12.1 76.8 3.6 3.3 1.1 2.0 0.8 0.3 389 Comparative Catalyst E 6.0 2.4 4.738.9 5.9 12.1 13.2 16.8 183 Example 1

TABLE 3 Catalyst type Dispersibility in water Example 1 Catalyst A AExample 2 Catalyst B A Example 3 Catalyst C A Example 4 Catalyst D AComparative Example 1 Catalyst E D

From Table 2, it was found that the proportion of small particles issmall and the mass average particle diameter is reasonably large withrespect to polyalkylene oxide particles obtained in Examples.Furthermore, from Table 3, it was found that polyalkylene oxideparticles obtained in Examples have an excellent dispersibility inwater.

The invention claimed is:
 1. A production method of polyalkylene oxideparticles, comprising: forming polyalkylene oxide particles bypolymerization of an alkylene oxide in a polymerization solutioncontaining a polymerization solvent and a catalyst dispersed in thepolymerization solvent, wherein the catalyst is an organozinc catalystin a form of particles having an average particle diameter more than 25μm.
 2. The production method according to claim 1, wherein theorganozinc catalyst is a particulate reaction product obtainable by amethod including: reacting an organozinc compound with an aliphaticpolyhydric alcohol and a monohydric alcohol, thereby forming aparticulate reaction product.
 3. The production method according toclaim 1, wherein the polymerization solution contains 0.00005 mol ormore of the catalyst with respect to 1 mol of the alkylene oxide. 4.Polyalkylene oxide particles obtainable by the production methodaccording to claim 1, wherein the proportion of particles having aparticle diameter less than 150 μm is 0.7% or more and less than 30% bymass.